This invention relates to the manufacture of a multi-layered liquid crystal display panel.
In recent years, a substantial amount of effort in the field of liquid crystal matrix displays has been devoted to the development of a high-density multi-line display, aiming at an improvement in image quality. Liquid crystal displays with matrix-shaped electrode structures are quite favorable to fulfill a power saving demand because of their capability of being excited with low power consumption.
One way in which the above-mentioned matrix type liquid crystal displays are excited is the line sequential scan method as depicted in FIG. 1, for example. After characters, symbols and so forth are converted into desired display patterns via a character signal converter 2 and loaded into a buffer memory in a column drive circuit 3 row by row with respect to a display screen a main storage 1 supplies its outputs to row electrodes Y.sub.1, Y.sub.2 . . . Y.sub.n, respectively. The information thus stored in the buffer memory appears on the display screen row by row. A control circuit 5 commands the column drive circuit 3 and a row drive circuit 4. As stated above, a liquid crystal display panel 6 has a matrix type electrode structure.
For the matrix type liquid crystal display panel the greater the number of the rows (scanning line number), the higher the density and accuracy of display. However, with an increase in the number of the rows, the length of time at which a signal is applied per column, a duty factor, would be shortened and the problem arises that crosstalk takes place. In particular, liquid crystal display devices show dull threshold characteristics and slow response characteristics, resulting in difficulty in obtaining satisfactory contrast. There are several attempts to overcome these problems:
(1) The development of liquid crystal material having more definite threshold properties, PA1 (2) A matrix address scheme in the optimum condition with an extended operating margin (.alpha.=V.sub.on /V.sub.off), and PA1 (3) The design of an electrode structure with a seemingly higher resolution. PA1 (a) double electrode structure PA1 (b) vertical partition, and PA1 (c) two-layered structure.
Though the first two attempts (1) and (2) do not need to modify largely the well known structure of liquid crystal cells, it appears almost impossible to increase drastically the number of excitable lines from the viewpoint of the present-day progress of liquid crystal materials, etc. Contrarily, the last method (3) has the problem that liquid crystal cells are complicated in construction but is actually possible to increase the number of excitable lines twice, three times, four times and so forth.
Typical ways of making possible the last approach (3) are as follows:
Those ways may be adopted alone or in combination for achieving the purpose. Such combination has been proposed by co-pending application Ser. No. 921,062 filed June 30, 1978, MATRIX TYPE LIQUID CRYSTAL DISPLAY PANEL by F. Funada et al.